A bow thruster is a device that lets a boater more easily position a boat in difficult situations like docking and maneuvering in congested marinas. A bow thruster delivers a side-directional thrust force for maneuvering the boat. Bow thrusters generally operate on the principal of creating force to counteract the unwanted lateral swinging of the bow of the boat to stabilize the lateral position of the boat. The bow thruster must be sized to provide a thrust force that is sufficient under all sorts of weather and water conditions. Conventional bow thrusters typically involve positioning a motorized propeller beneath the water line adjacent the bow, where rotation of the propeller blade can be controlled to counteract the unwanted lateral movement of the bow. However, permanent modifications to the boat are normally necessary in order to attach these bow thrusters to existing boats that were built without this device in mind.
A variety of bow thruster and related devices are known in the art. For example, U.S. Pat. No. 4,208,978 discloses a bow thruster for a water vessel that may be attached to existing vessels and has a submersible pumping unit for producing lateral thrust. The submersible pumping unit consists of a rotary hydraulic motor driving an axial float pump, with both the motor and the pump being mounted in a flow-through housing that can be lowered into the water or raised out of the water by a hydraulic cylinder piston unit mounted on the exterior of the vessel's hull at the bow. A motor-driven pump on board the boat operates the hydraulic motor through flexible hoses. The submersible pumping unit has separate valves at the water intake and discharge sides of its pump for controlling the magnitude of the lateral thrust.
U.S. Pat. No. 4,732,104 discloses a pivotal bow thruster that may be transferred from boat to boat. The unit consists of a motor and two propellers, the unit being pivoted about the stem of the boat by being connected to a pivoting means. When the unit is in the lower active position, the propeller is actuated to rotate in one direction or another, thereby thrusting the bow of the boat in a particular lateral direction.
U.S. Pat. No. 4,807,552 discloses a small boat bow thruster that includes a port and a starboard discharge nozzle mounted through the hull of the boat above the water line. An inlet port is located at the boat hull below the water line, providing an inlet for water direction by a bi-directional water pump. The water pump is connected between the inlet part of the starboard side and port side outlet nozzles. Rotation of two rotors produces water flow from the inlet port through the starboard side outlet nozzle allowing the bow to be thrust to the port side, while rotation of the rotor is in the opposite direction produces the water flow from the inlet port through the port side nozzle allowing the bow to be thrust to the starboard side. The port and starboard nozzle exit from the boat hull above the water line and impinge on the surrounding water.
U.S. Pat. No. 6,024,038 discloses a side thruster for a small boat, which includes a valve, four water passageways, and a pump. One passageway extends between the first port and a side opening of the boat. The second passageway extends between the third port and another side opening. The third passageway extends between the second port and the pump outlet. The fourth passageway extends between the pump inlet and a pump fourth port. When the barriers move to a first position, the pump draws water from the second side opening and discharges the water through the first side opening. Conversely, when the barriers move to its second position, the pump draws water from the first side opening and discharges the water from through the second side opening. These side openings are located on the bow of the boat.
U.S. Pat. No. 6,363,874 discloses a rotational electric bow thruster for recreational water craft. This system includes a rotatable thrust assembly, which includes a prop or props coupled to and rotatable with the assembly. The prop is further coupled to a power transmission drive train, which is powered by a drive motor. The rotatable assembly is further coupled to an angular drive configured for orienting the prop to produce a thrust in a desired direction during operation.
U.S. Pat. No. 6,361,387 discloses a bow thruster comprising an impeller disposed in a tunnel at the bow of the vessel.
Although the above devices may provide side-directional thrust movement for water vessels, they are not without deficiencies (i.e., some are not portable, some require holes to be drilled in the hull, etc.) and further improvement is needed. More particularly, there is a need for a portable bow thruster that can be easily retrofitted to an existing boat without the need for any holes through the hull for flow, mounting, or electrical wires.